Oscillometry (OS) measures lung function with minimal patient effort, complements traditional physiology, yet is infrequently used. There are no reports of oscillometry from community practice. We wished to 1) determine if OS is feasible in community practice, 2) examine OS characteristics by GOLD stage and grade, and 3) correlate OS parameters with COPD assessment test (CAT) and mMRC dyspnea scale.
Subjects from a community respirology practice with COPD, ≥10 pack-year smoking history, and either a post bronchodilator FEV1/FVC<0.70 (GOLD), MMEF<65% predicted or RV>130% predicted (non-GOLD), and healthy controls (HC) recruited from clinic staff, underwent 3-5 measurements of forced OS (tremoFlo C-100, 5-37Hz, Thorasys, Montreal, QC, Canada) when well. From 3 tracings with a coherence at 5 Hz (COH5) of >0.6, resistance at 5 Hz (R5), frequency dependence of resistance (R5-19), reactance at 5 Hz (X5), resonance frequency (Fres), reactance area (AX) and inspiratory-expiratory X5 (ΔX5) were calculated for each subject. Annual spirometry and CAT questionnaires and acute exacerbations rates (AER) were abstracted from charts. Subjects were divided into GOLD stages and grades and compared with non-GOLD COPD and HC. Differences for biometrics and spirometry were determined with ANOVA. Differences in OS parameters were determined using Kruskal-Wallis tests and between groups using Mann-Whitney tests Holm’s corrected for multiple comparisons. Spearman rank correlations were determined for both CAT and mMRC dyspnea scale, vs. spirometry and OS parameters.
COH5 was >0.6 in 307/311 COPD (99%) and 21/21 HC (100%). ΔX5 could be calculated in 286/307 COPD subjects (93%) and 20/21 HC (95%). Age, sex distribution, smoking history and BMI were similar between GOLD stages and grades. There were significant perturbations of all OS parameters by increasing GOLD stage and grade (Kruskal-Wallis p<0.001) but only for stage were these differences significant between adjacent groups (Mann- Whitney p<0.0001-0.0018). While weak, CAT correlated best with Ax (0.319, p<0.001) and mMRC with FEV1 (-0.361, p<0.001). Dyspnea sub-questions (3 and 4) of CAT and Ax correlated best (0.372, p<0.001).
OS is feasible in community practice. In this small COPD population, OS parameters worsen more with increasing GOLD stage than grade and correlate better than spirometry with CAT but not mMRC.
OS offers an alternative measure of lung function particularly useful in patients unable to perform spirometry.